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Evaluation of residual neuromuscular blockade using modified double burst stimulation
Y Saitoh1, K Nakazawa, K Makita
1Department of Anesthesiology and Critical Care Medicine, Faculty of Medicine, Tokyo Medical and Dental University, Japan.
Background:
To assess the degree of residual neuromuscular blockade, double burst stimulation (DBS) is commonly applied in the clinical setting. However, fades in response to DBS3,3 can rarely be identified manually when train-of-four (TOF) ratios are > or = 0.70, and, in contrast, fades in response to DBS3,2 are felt manually in an undesirably high proportion of cases, even at TOF ratios greater than 0.7. We investigated whether a new monitoring method, modified DBS, would be useful to determine an adequate degree of recovery from neuromuscular blockade. For modified DBS, two burst stimuli were applied at an interval of 750 ms. The first stimulation in the modified DBS consisted of two stimuli of 0.3 ms duration at 50 Hz and the second of two stimuli of 0.2 ms duration at 50 Hz.
Methods:
Forty-five adult patients undergoing elective nitrous oxide-oxygen-isoflurane anesthesia were randomly divided into one of three groups: DBS3,3 group (n = 15), DBS3,2 group (n = 15), or modified DBS group (n = 15). During recovery from vecuronium-induced neuromuscular blockade, on both forearms, DBS3,3, DBS3,2, and modified DBS were delivered in the DBS3,3 group, DBS3,2 group, and modified DBS group, respectively. One hand and forearm (fixed arm) were immobilized to quantify the degree of neuromuscular blockade mechanically, and the contralateral arm (free arm) was unrestrained. An observer determined tactiley on the free arm the presence or absence of fade in response to the three DBS patterns.
Results:
Probabilities of detection of fade in response to the DBS3,3 were 67% (TOF ratio of 0.51-0.60), 40% (0.61-0.70), 19% (0.71-0.80), 5% (0.81-0.90), and 0% (0.91-1.00). Those to the DBS3,2 were 95% (0.51-0.60), 93% (0.61-0.70), 83% (0.71-0.80), 65% (0.81-0.90), and 38% (0.91-1.00). Those to modified DBS were 90% (0.51-0.60), 86% (0.61-0.70), 65% (0.71-0.80), 25% (0.81-0.90), and 3% (0.91-1.00). Those modified DBS was more sensitive in diagnosing residual neuromuscular blockade than DBS3,3 at the TOF ratio of 0.51-0.90, but was less sensitive than DBS3,2 at the TOF ratio of 0.81-1.00 (P < 0.05).
Conclusion:
Our results indicate that the modified DBS may be a useful stimulation pattern to diagnose the adequacy of recovery from neuromuscular blockade.